In plants equipped with clean rooms, very high demands are placed on the purity of the ambient air. Air that is purified of dust and microorganisms is necessary, in order to maintain the desired level of air purity. In addition to filter mats and bag filters, so-called cartridge filters are a common type of air filter design. A conventional type of cartridge filter design has a fold pack that is oriented perpendicularly to the direction of flow and is provided with an outer frame. The fold pack and the frame are sealed from one another by a sealing material. The fold packs themselves are made of accordion-fold filter paper. Under conditions involving suspended particulate matter, plastics, which are mostly processed in liquid form, are used as sealing material. When working with filters for fine particulate matter, a filter fleece can also be inserted as sealing material.
The outer frame gives the filter the requisite mechanical stability, protects the fold pack from damage, and allows the filter element to be inserted into a holding fixture in a sealing-seat type of installation. The individual filter frames are assembled from four frame strips, the use of corner connectors also being additionally possible.
Cartridge filters are requested by customers in virtually all possible dimensions and design variants. This leads to a very cost-intensive single-part production, in particular of the frame strips, since each dimension necessitates a separate deep-drawing die or casting mold.
The German Patent Application DE 195 45 064 A1 describes a filter insert which can be described as a cartridge filter. The filter insert is made of a filter frame and a fold pack, the latter being arranged gas-imperviously in the filter frame by a seal along its outer periphery.
The German Patent DE 195 45 046 C2 describes a fold pack design for insertion into a cartridge filter.
In the not previously published German Patent Application DE 101 37 926.9, a cartridge filter is discussed, whose frame is made of profiled strips of the same design and of corner connectors that grasp the profiled strips at the end pieces thereof. This cartridge filter has the advantage that the frame can be manufactured very simply with very different dimensions. The frame can be assembled from profiled strips, from cut-to-length sections of a continuously extruded profile, in any desired size. This means that the height and width of the frame can be varied as needed when working with a predefined form of a profiled strip. However, the depth of the cartridge filter, i.e., the dimensions from the inflow side to the outflow side of the air, is predetermined by the width of the profiled strip.